Manufacture of organic polysulfides



Patented Mar. 22, 1949 MANUFACTURE OF ORGANIC POLYSULFIDES John L.Eaton, Trenton, Mich., as'signor to Sharples Chemicals Inc., acorporation of Delaware No Drawing. Application July 3, 1945,- SerialNo. 603,113

11 Claims. 1

The present invention pertains to oxidation oi organic compounds havingan SM radical, M designating ammonium or substituted ammonium radical, ametal or hydrogen, and S designating sulfur. It was developed primarilyas a process for obtaining tetra-alkyl thiuram disulfides by oxidationof salts of dialkyl dithiocarbamic acids and it Will accordingly bedescribed first with reference to that problem.

In an article in the Canadian Journal of Research, volume 2, pages144-52 (1930), Cambron and Whitby have described a process by which asalt of diethyl dithiocarbamic acid is oxidized with a nitrous acid saltat C. by addition of a dilute mineral acid to produce the desiredtetraethyl thiuram disulfide, in accordance with the following equation:

Cambron and Whitby discussed this reaction. on page 151 of theirarticle, describing. anexperiment involving treatment of a mixturecontaining 45 grams of. the sodium salt of diethyl dithiocarbamic acidand 18 grams of sodium nitrite in; 100 cc. of water with 80 cc. of a 25%hydrochloric acid solution. They noted the fact that the crystallizedtetra alkyl' thiuram disulfide obtained' by this process had a meltingpoint. of 71 C. and was a relatively pure product, but made no commentwith respect to the conversion or" yield obtained in the: practice ofthe process.

As mentioned in the patent to-Olin and Deger, 2,325,194, neither theyield nor conversion obtained in practice of the Cambrcn andWhitbyprocess is particularly high. A substantial improvement in aprocess of this general character has been made by- Olin and Deger, asdescribed and claimed in their: Patent 2,325,194, whereby theseconversions and yields are much increased. In the practice of theprocess of said Olin and Deger patent, methyl, ethyl, propyl, isopropyl,butyl, or a. higher alcohol is mixed with a nitrous acid saltand thesalt of the dialkyl dithiocarbamicacidto be oxidized, and the resultantmixture is cooled. whilera dilutesolution of a mineral acid (e. g,sulfuric, hydrochloric or phosphoric acid) is gradually added. As taughtby Olin and Deger, the nitrous acid is believed to be first convertedinto the corresponding alkyl nitrite. and this alkyl. nitritethereafterserves as the oxidizi'ng agent, as illustrated by thefollowing equations:

21103 2NaNO2 21101 ZRONO 21 120 ZNaCl 2R ONO. ZNaSGSNRy-l- 2H0]. 5:

s s REN SSI NRQ ZROH mo e 2Na0 In the oxidation of salts of dialkyldithiocar- 2 bamic acids in practice of the present invention, as inpractice or the invention of the Olin and Deger patent, it is preferablethat an aliphatic alcohol, such as methyl alcohol. or one of the otheralcohols mentioned. above, be employed in addition to the nitrous acidsalt and the mineral acid. Regardless of Whether an. alcohol or alkylnitrite is employed, however, or whether a mixture of an alkyl nitriteWith an. inorganic saltof nitrous acid is employed, substantialadvantageis obtained by practice of the oxidation reaction in accordancewith the modified order of pro'-- cedure of the present invention.

The present invention rests upon the discovery that, inan oxidationreaction of this type, the formation of the desired organicpolysulfi'd'e may be substantially improved, from the standpoint. ofconversion, yield, and economy of materials, by the addition of themineral acid and. the or:- ganic compound to be oxidized separately andprogressively into-an aqueous solution of the ox idizing agent. In themanufacture of tetra=alkyl thiuram disulfides by oxidation ofsalts'ofdialkyl'i dithiocarbamic acids'inaqueous solution, for-1' ex ample. ithas been found that the yield can be increased considerably, thequantity of aliphatic alcohol required to obtain. best resultsreducedby" as much as and the quantity of oxidizing. agent necessary toaccomplish the oxidation. re duced, by the: simple change in procedurein volved in: maintaining a body of. the oxidizing. agent and.introducing. the aqueous solution: of dithiocarbamic acid salt andmineral acid separately and progressively into" this body of oxidizingagent.

In. the practice of the. invention, there is first introduced into thereactionv vessel an aqueous solution of the oxidizing: agent. Thisoxidizing agent may be an. alkyl. nitrite, a saltof. nitrous acid, ora.mixture of a nitrous. acid. salt with an: alkyl nitrite; Inaccor'dancewith preferrad pro? cedure, a nitrous acid salt and: analiphatic? alcohol are: introduced into the. reaction: vessel. andserve: as. the oxidizing. medium. Separate aqu'e'e oussolutions of the:dithio'carbamic acid salt to be oxidized (e. g., the. sodium salt of.diethyl dithio' carbamic acid)? and: of the mineral. acid (hydro chloricacid) are then introduced progressively" at such relativeratesthat thereaction mixture contains a moderate concentration: of unbxidiz'ed'dithiocarbamici acid salt until the finer stage" of the:rea'cticn.Inithecasesof use of anitrous' aci'd salt as the oxidizingv agent and asalt of the dithiocarbamic acid as thematerialto be oxidized; there willof course: be formed twomoleculesof basic constituents ioreach moleculeofthiura mdisulfide formed, and itis; of course", desirable that thesebasic. constituents be entirely new tralized. In practice: of theinventionghovvever, itiis best thatthe quantity of Iminer alaIcid addedlag somewhat behind the stoichiometric quantity which would be necessaryfor neutralization of the theoretical quantity of basic constituentsformed if the entire body of dithiocarbamic acid salt were to beoxidized; i. e., in the particular case under consideration, thequantity of hydrochloric acid should be less than double the molecularquantity of dithiocarbamic acid salt introduced. After the totalquantity of dithiocarbamic acid salt to be oxidized has been introduced,it will, of course, be desirable that the oxidation reaction be carriedto completion and the neu-- tralization of liberated basic constituentscompleted by addition of a further quantity of mineral acid suflicientto accomplish completion of the oxidation and. neutralization of thebases liberated incident to such completion.

In line with the discussion of the detailed procedure explained in thelast preceding paragraph, it should be pointed out that one excellentway to assure maintenance of a stoichiometric excess of the organiccompound to be oxidized, as compared to the mineral acid introduced, isto first introduce a part of the organic compound to be oxidized intothe aqueous solution of oxidizing medium, and then to introduce themineral acid and further material to be oxidized, this subsequentintroduction taking place progressively and simultaneously, and inapproximately the proportions in which the material to be oxidized andthe mineral acid enter into the reactions of oxidation andneutralization with which we are concerned. Thus, in the oxidation ofsalts of dialkyl dithiocarbamic acids, a minor portion of such salt mayfirst be introduced into the aqueous solution of oxidizing medium, andthe remainder may thereafter be introduced simultaneously with themineral acid, a relative rate of introduction of two moles of mineralacid for each mole of the salt of the dithiocarbamic acid salt beingmaintained during such subsequent introduction until all of thedithiocarbamic acid salt to be oxidized has been introduced and untilthe reaction has gone fairly far toward completion. When this stage hasbeen reached, the remainder of the mineral acid necessary to produce theultimate degree of oxidation and neutralization is then graduallyintroduced, without further introduction of other reactants.

While the invention has been described above in reference to formationof thiuram disulfiides, it should be understood that this invention isby no means limited to this one specific problem but is applicablegenerally to organic oxidation reactions of this type, as discussed inthe aforementioned Olin and Deger Patent 2,325,194. Thus, the generalorder of procedure herein discussed may be employed in the manufactureof xanthogen disulfides by oxidation of xanthates, in the manufacture ofdithiocarbonic acid, didithiocarbonic acid and di-trithiocarbonic acidfrom the corresponding mono-, di-, and trithiocarbonic acids,respectively, and in the manufacture of disulfides from mercaptans.

, Futhermore, although the invention may advantageously be practiced bythe maintenance of a relatively small excess of carbamate during themajor part of the oxidation, it is to be understood that the presence ofevenvhigher relative concentrations will lead to results which are morefavorable than when the entire quantity of oxidizable material ischarged initially.

The following examples illustrate the practice of this invention asapplied in manufacture of 4 tetra-alkyl thiuram disulfides and willteach the person skilled in the art, when they are considered inconjunction with the examples of the aforesaid Olin and Deger patent, topractice the invention in oxidation of these other sulfhydrylderivatives.

Example I 2 moles of the sodium salt of diethyl dithiocarbamic acid,dissolved in 70 moles of water, were oxidized to form tetra ethylthiuram disulfide by treatment with 2 moles of sodium nitrite and 4moles of hydrogen chloride in the presence of one mole of methanol, asfollows. To a charge consistingof all the methanol, all the sodiumnitrite, and 30% of the sodium diethyl dithiocarbamate dissolved inwater there were gradually introduced at uniform rates over a period ofone hour aqueous solutions containing all the remainder of the sodiumsalt of diethyl dithiocarbamic acid and hydrogen chloride. The relativerates of introduction of these subsequently added aqueous solutions wassuch that an excess of the salt to be oxidized was constantly maintainedin the reaction mixture and that the addition of the dithiocarbamic acidsalt was completed when only of the theoretically required (double thestoichiometric) amount of hydrogen chloride had been added. Theremainder of the necessary hydrochloric acid solu-' tion was then addedgradually in order to complete the reaction. The reaction mixture wasagitated vigorously and cooled during the practice of the process ofthis example as described above in order to maintain the temperature atapproximately 20 C. throughout the reaction. The yield of the desiredtetraethyl thiuram disulfide was 99%.

Comparative Example II This example is given for the purpose ofproviding a comparison between the process of Olin and Deger Patent2,325,194, and the process of the present invention. It should becompared to Example III, below. A batch of sodium diethyldithiocarbamate solution was prepared by the action of diethyl amine ona mixture of carbon disufilde and aqueous caustic soda. 2 moles of thissolution (containing 65 moles of water) were charged into a reactor, and2 moles of sodium nitrite and 2 moles of methanol were added. To thissolution, held at 25 C., and agitated, was introduced 4 moles of 66 B.1101 over a period of 45 minutes. disulfide was 89%.

Example III Using the same carbamic acid salt solution as in Example IIand the same proportions of re- Example IV A run was made which wassimilar in all respects to that described in Example III, except thatone mole of methanol was used instead of two. The yield of tetra ethylthiuram disulflde was 97%.

The yield of tetra ethyl thiuram- Example V A run was made which wassimilar in all respects to that described in Example III except thatonly half of the quantity of methanol and three-quarters of the quantityof sodium nitrite used in that example were employed. The yield of tetraethyl thiuram disulfide was 91%.

Various modifications are available to those skilled in the art, and Ido not therefore wish to be limited except by the scope of the followingclaims.

I claim:

1. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducingsaid salt and a mineral acid separately and progressively into anaqueous solution of an oxidizing agent chosen from the class consistingof salts and alkyl esters of nitrous acid, and mixtures of said saltsand esters, the respective rates of introduction of said mineral acidand of said first-mentioned salt being regulated with respect to eachother such as to maintain in the reaction mixture an unreacted portionof said first-mentioned salt until such time as the introduction of saidfirst-mentioned salt is discontinued.

2. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducingsaid salt and a mineral acid separately and progressively into anaqueous solution of a nitrous acid salt and methyl alcohol, therespective rates of introduction of said mineral acid and of saidfirst-mentioned salt being regulated with respect to each other such asto maintain in the reaction mixture an unreacted portion of saidfirst-mentioned salt until such time as the introduction of saidfirst-mentioned salt is discontinued.

3. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducingsaid salt and a mineral acid separately and progressively into anaqueous solution of a nitrous acid salt and an aliphatic alcohol, therespective rates of introduction of said mineral acid and of saidfirst-mentioned salt being regulated with respect to each other such asto maintain in the reaction mixtur an unreacted portion of saidfirst-mentioned salt until such time as the introduction of saidfirst-mentioned salt is discontinned.

4.. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducingsaid salt and a mineral acid separately and progressively into anaqueous solution of an alkyl nitrite, the respective rates ofintroduction of said mineral acid and of said first-mentioned salt beingregulated with respect to each other such as to maintain in the reactionmixture an unreacted portion of said first-mentioned salt until suchtime as the introduction of said first mentioned salt is discontinued.

5. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducing aquantity of said salt into an aqueous solution of an aliphatic alcholand an oxidizing agent comprising a salt of nitrous acid, thereafterintroducing further quantities of said first-mentioned salt and of amineral acid separately and progressively into said aqueous solution,the respective rates of introduction of said mineral acid and of saidfirst-mentioned salt being regulated with respect to each other such asto maintain an unreacted portion of said first-mentioned salt until suchtime as the introduction of said first-mentioned salt is discontinued,and thereafter continuing the addition of said mineral acid toneutralize basic constituents formed incident to the oxidation reaction.

6. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocar- .bamic acid, the process comprising introducinga quantity of said salt into an aqueous solution of an aliphatic alcoholand an oxidizing agent comprising a salt of nitrous acid, and thereafterintroducing further quantities of said first-mentioned salt and of amineral acid separately and progressively into said aqueous solution,the addition of said first-mentioned salt and of said mineral acid beingcontrolled at such rate that the quantity of said first-mentioned saltin the solution is maintained in stoichiometric excess of the quantityof mineral acid in said solution until substantially the entire quantityof said salt to be oxidized has been introduced into said solution.

7. In the manufacture of a thiuram disulfide by the oxidation of a saltof a dialkyl dithiocarbamic acid, the process comprising introducing aquantity of said salt into an aqueous solution of an aliphatic alcoholand an oxidizing agent comprising sodium nitrite, and thereafterintroducing further quantities of said first-mentioned salt and of amineral acid separately and progressively into said aqueous solution,the addition of said first-mentioned salt and of said mineral acid beingcontrolled at such rate that the quantity of said first-mentioned saltin the solution is ma ntained in stoichiometric excess of the quantityof mineral acid in said solution until substantially the entire quantityof said salt to be oxidized has been introduced into said solution, anda further quantity of the mineral acid being thereafter added until aquantity of mineral acid has been added which is suiiicient toneutralize basic con-- stituents formed incident to the oxidationreaction.

8. In the manufacture of tetraethyl thiuram disulfide by the oxidationof a salt of diethyl dithiocarbamic acid, the process comprisingintroducing said salt and a mineral acid separately and progressivelyinto an aqueous solution of a salt of nitrous acid and a saturatedaliphatic monohydric alcohol having less than 5 carbon atoms, therespective rates of introduction of said mineral acid and of saidfirst-mentioned salt being regulated with respect to each other such asto maintain in the reaction mixture an unreacted portion of saidfirst-mentioned salt until such time as the introduction of saidfirst-mentioned salt is discontinued.

9. In the manufacture of tetramethyl thiuram disulfide by the oxidationof a salt of dimethyl dithiocarbamic acid, the process comprisingintroducing said salt and a mineral acid separately and progressivelyinto an aqueous solution of a salt of nitrous acid and a saturatedaliphatic monohydric alcohol having less than 5 carbon atoms, therespective rates of introduction of said mineral acid and of saidfirst-mentioned salt being regulated with respect to each other such asto maintain in th reaction mixture an unreacted portion of saidfirst-mentioned salt until such time as the introduction of saidfirst-mentioned salt is discontinued.

10. The process of claim 8 in which the firstmentioned salt is thesodium salt of diethyl di- UNITED STATES PATENTS thiocarbamic acid, inwhich the mineral acid is hydrogen chloride, and in which the salt ofni- Numbe Name Date trous acid is sodium nitrite. 1,903,935 Tschunkul y1933 11. The process of claim 9 in which the mineral 5 2,325,194 01inJuly 27, 1943 acid is hydrogen chloride, and in which the salt OTHERREFERENCES of nitrous acid is sodium nitrite.

JOHN EATON. Cambron, et al., Canadian Journal of Research," vol. 2, page151. (Copy in Scientific Li- REFERENCES CITED m brary.)

The following references are of record in the file of this patent:

